Recently, a Fan-out WLP structure or the like, which connects a semiconductor chip having an integrated circuit with a printed circuit board by fine wiring, are being developed for the purpose of miniaturization of the printed circuit board in order to meet requirements of a reduction in size, an improvement of performance, and a reduction in costs of an electronic device.
In order to implement the formation of a fine wiring on a printed circuit board at a low cost, a forming method is under consideration in which only a fine wiring circuit part is formed on a support board and the fine wiring circuit part is transferred onto the printed circuit board. As a method of improving the strength of the fine wiring circuit part, a method of forming a through electrode in a resin board has been developed.
A circuit board is formed by using the resin board including a through electrode therein and providing, on the resin board, a fine wiring layer having wiring connected with an electrode surface of the through electrode exposed from a surface of the resin board. However, in this case, electric field concentration is generated at an end portion of the electrode surface of the through electrode due to an edge effect. Due to the electric field concentration, there is a problem in that material interfaces between the fine wiring layer and the resin board having low voltage resistance coincide each other, and as a result, a short-circuit occurs. The short-circuit considerably degrades the reliability of the circuit board.
The followings are reference documents.
[Document 1] Japanese Laid-Open Patent Publication No. 2004-146602,
[Document 2] Japanese Laid-Open Patent Publication No. 2005-142267,
[Document 3] Japanese Laid-Open Patent Publication No. 2001-102477,
[Document 4] Japanese Laid-Open Patent Publication No. 2007-081433,
[Document 5] Japanese Laid-Open Patent Publication No. 2008-270346, and
[Document 6] International Publication Pamphlet No. WO 2009/088000.